The present invention relates to a hair drier and more particularly to a hair drier that incorporates a brushless motor.
A hair drier primarily includes a heater bobbin on which a heater is wound, a wind tunnel having a wind guide, a commutator motor fixedly mounted to a holder disposed in the middle of the wind tunnel, and a fan fixed to a shaft of the commutator motor.
The commutator motor is an article that is assembled as a complete motor. The commutator motor is fixed on the holder mounted on the hair drier. As is disclosed, for example, in Japanese Patent Preliminary Publication (KOKAI) No. 8-343, the commutator motor extends from the holder, approaching the heater bobbin. This is because the commutator motor extends closer to an outlet than the holder due to the fact that overall length of the commutator motor is great by structural nature. This fact necessitates that the heater bobbin is shifted toward the outlet or the wind tunnel is shifted toward an inlet. As a result, the hair drier requires a larger housing.
The dc motor is connected to diodes that convert an ac voltage into a dc voltage. A commutator motor has diodes soldered to its feeding terminals. This implies that the hair drier should have a space in which the diodes are housed.
A commutator motor generates sparks because of mechanical contact of the brush with the rotor. The sparks enter television receivers and radios, creating nuisance noises in their audio outputs as well as disturbing video images.
The brush slowly wears out and the build-up of carbon particles may cause poor contact, causing decreased rotational speed or even a stoppage of the motor.
A commutator motor as a complete article is excellent in terms of assembly efficiency but a metal case that covers the motor adds a significant weight to the overall weight of a hair drier. In addition, the metal case does not provide the sufficient shielding effect against spark noise.
The recent trend is that users want to quickly dry their hair. Thus, high power heaters such as 1.2 kW and 1.3 kW are used and the fan speed is increased accordingly to provide larger volume of air.
Increasing the motor speed increases the volume of air as well as noise. This noise grates on the user""s ears.
Noise generated by a hair drier is divided into two groups; noise generated by mechanical contact between the brush of the motor and electrodes and acoustic noise created when the rotating fan cuts the air. The former is an uncomfortable buzz and the brush deteriorates significantly. The latter is due to the principle that a motor drives a fan to produce wind.
Use of a brushless motor may be a solution to brush noise that grates on the user""s ears.
However, the brushless motor eliminates noise due to the brush but provides less volume of air. This is because a brushless motor has a small initial torque and therefore the rotational speed is selected to be relatively low.
The present invention was made in view of the aforementioned problems.
An object of the invention is to provide a hair drier in which the motor does not generate significant noise and have a long life, and the noise from the motor does not enter televisions and radios to disturb the outputs thereof.
Another object of the invention is to provide a light weight hair drier in which parts of a motor are formed integral with parts of a drier.
Still another object of the invention is to make a compact drier having a housing with shorter overall length and yet accommodating and fixedly supporting the heater bobbin, motor, and fan therein.
A further object of the invention is to employ a brushless motor for less noise and yet for larger volume of wind.
In order to solve the aforementioned problems of the conventional art, a hair drier according to the present invention is characterized by:
a longitudinally extending cylindrical housing having an inlet and an outlet so that air flows from the inlet to the outlet;
a heater section disposed in said housing close to said outlet; and
a wind supplying unit disposed between the heater section and the inlet;
wherein the wind supplying unit includes a holder in line with an axis that extends in a longitudinal direction of the housing and a base rotatably mounted on the holder, the base having a plurality of vanes that are disposed about the axis and radially extend from the axis;
wherein the holder has a stator with a plurality of winding units disposed around the axis, and the base has a rotor disposed around the axis such that the rotor surrounds the stator, the rotor and stator forming a brushless motor.
The holder has a plurality of wind guides that are fixed on an inner wall of the housing and radially extend, the wind guides serving to guide a flow of air generated by the plurality of vanes toward the heater section.
The base is substantially in the shape of a cylinder having an inner surface that defines an opening, the base having the rotor fixed to the inner surface and rotatably fitting over the holder.
The rotor has a dimension in a direction parallel to the axis selected to be larger than that of the stator, and the stator and rotor are positioned relative to each other such that the center of the stator in the direction parallel to the axis is at the same position as that of the rotor.
The base has a shaft and the holder has a bearing into which the shaft is inserted, the bearing is disposed closer to the outlet than the stator.
The holder has a space formed therein that accommodates a drive circuit for supplying electric power to the winding units.
The opening has an inner diameter larger than an outer diameter of the holder, so that the opening fits over the holder.
The heater section includes a heater bobbin having two insulating boards assembled together to form the shape of a cross, and a heater wire wound around the heater bobbin, wherein the heater bobbin has a diode mounted thereon for producing a d-c voltage supplied to the stator, the diode being supported across the insulating boards and being close to the holder.
A heat-shielding plate is placed between the insulating boards and the holder to isolate the diode from the holder.
The diode is a molded article having a plurality of elements therein, the article being mounted to one of the insulating boards.